Human Anatomy Vol 1

THORAX

Anterior longitudinal ligament

Middle band of the radiate

ligament forming hypochordal bow

Posterior longitudinal ligamenl

Costovertebral joint

lnferior costotransverse

ligament

Costotransverse joint

Lateral costotransverse

ligament

Fig. 13.5: Attachments and articulations of the posterior end of
a typical rib

Anterior longitudinal ligament lntra-articular

ligament

Radiate ligament

Middle band of radiate

ligament forming

hypochordal bow

Fig. 13.6: The superior costotransverse, radiate and intra-

articular ligaments

angle also separates the origin of external oblique

from that of latissimus dorsi in case of ninth and

tenth ribs.

b. The internal intercostal muscle arises from the floor

of the costal groove. The intercostalis intimus arises

from the middle two-fourths of the ridge above

the groove. The subcostalis is attached to the inner

surfaces of the lower ribs (see Fig. 74.2).

c. The external intercostal muscle is attached on the

outer lip of the upper border, while the internal

intercostal and intercostalis intimi are attached on

the inner lip of the upper border.

A typical rib ossifies in cartilage from:

a One primary centre (for the shaft) which aPPears/

near the angle, at about the eighth week of

intrauterine life.

b Three secondary centres, one for the head and two

for the tubercle, which appear at puberty and unite

with the rest of the bone after 20 years.

First Rib

1 It is the shortest, broadest and most curved rib.

2 The shaft is not twisted. There is no costal groove.

3 It is flattened from above downwards so that it has

superior and inferior surfaces; and outer and inner

borders.

1 The anterior end is larger, thicker and pitted. The

posterior end is small and rounded.

2 The outer border is convex and not having costal

groove.

3 The upper surface of the shaft is crossed obliquely

by two shallow grooves separated by a ridge. The

ridge is enlarged at the inner border of the rib to form

t}:re scalene tubercle.

When the rib is placed on a horizontal plane, i.e. with

the superior surface facing upwards, both the ends of

the rib touch the surface.

Fesfures of f Rfb

1 The anterior end islarger and thicker than that in the

other ribs. It is continuous with the first costal

cartilage.

2 The posterior end comprises the following.

a. The head rs small and rounded. It articulates with

the body of first thoracic vertebra.

b. The neck is rounded and directed laterally,

upwards and backwards.

c. The tubercle is large. It coincides with the angle of

the rib. It articulates with the transverse Process

of first thoracic vertebra to f orm the

costotransverse joint.

3 The shaft (body) has two surfaces, uPPer and lower;

and two borders, outer and inner.

a. The upper surface is marked by two shallow

grooves, separated near the inner border by the

scalene tubercle.

b. The lower surface is smooth and has no costal

Sroove.

c. The outer border is convex, thick behind and thin

in front.

d. The inner border is concave.

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1 Anteriorly, the neck is related from medial to lateral

side to:

a. Sympathetic chain.

b. Posterior intercostal vein.

c. Superior intercostal arterY.

d. Ventral ramus of first thoracic nerve (Fig. 13.7).

(Mnemonic-chain pulling a VAN)